A marine radar beacon (racon) is a microwave transmitter which receives a radar pulse from a ship and provides a reply signal which locates and identifies the racon. Side lobe suppression refers to the capability of the racon to distinguish between the main lobe of the received signal and its low level side lobes in order to deny a response to the radar side lobes. A side lobe suppression circuit operates by storing threshold values in a side lobe suppression memory. This results in much less clutter, or false responses, being displayed on the radar screen. For input signals below this threshold, no transmission will occur, but for input signals above the threshold, the racon will transmit replies within a desired transmission band. However, the frequency edge band between in band and out of band frequencies is subject to temperature drift because of the dielectric properties of the frequency detection means.
The present invention is directed to determining frequency band edges as temperature varies and changing the frequency band transmissions in response to temperature variations.